It has long been recognized that compatible heterogeneous resin blends having good properties are characterized by the presence of finely dispersed phase and resistance to phase separation. Various methods have been reported to successfully enhance compatibility (see Xanthos, M. and S. S. Dagli, Compatibilization of Polymer Blends by Reactive Processing, in Polym. Eng. Sci., 1991, p. 929–35 and the articles cited there for an overview of the technology.) Reactive processing has long been recognized as means for attaining compatibility of polymeric blending partners. Enhancement of compatibility is known to be attained by forming copolymers, using reactive processing, such as graft or block copolymers with segments capable of specific interactions and/or chemical reactions with the blend components that would otherwise be incompatible. The review article referred to above points to continuous reactive processing, in particular, extrusion, as means to providing compatibilization of polymer blends through reactions during compounding. U.S. Pat. No. 3,856,886 disclosed thermoplastic graft copolymers wherein polymeric backbone contains aromatic hydroxy groups and where aromatic polycarbonate is grafted onto the backbone via the aromatic hydroxy groups. The disclosed graft copolymers are said to form blends with polycarbonate and/or with polymers of olefinically unsaturated monomers.
Graft polycarbonates in which the graft stock is a vinyl polymer which contains side chains that contain hydroxyphenyl groups, on which aromatic polycarbonate chains are condensed, have been disclosed in U.S. Pat. No. 3,991,009. These, together with graft polymer rubbers, form thermoplastic molding composition.
U.S. Pat. No. 4,874,816 disclosed a process for the production of vinyl copolymers with grafted-on polycarbonate chains. These grafts are prepared through the reaction of biphenols and phosgene in an interfacial process with hydroxyl containing vinyl polymers.